X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=src%2Fedu%2Fberkeley%2Fsbp%2FUnion.java;h=8f3ea2e428b6cbc8f1cc3da0d9cc6b7b7b6bb14c;hb=ce8452c48968090d71261ac773e39134ff764af4;hp=5932ac39ec7423a1c124afa28dc6eef896d0c2ab;hpb=24112db237318c030b4d4f457d90c34fd69d652b;p=sbp.git
diff --git a/src/edu/berkeley/sbp/Union.java b/src/edu/berkeley/sbp/Union.java
index 5932ac3..8f3ea2e 100644
--- a/src/edu/berkeley/sbp/Union.java
+++ b/src/edu/berkeley/sbp/Union.java
@@ -1,3 +1,5 @@
+// Copyright 2006-2007 all rights reserved; see LICENSE file for BSD-style license
+
package edu.berkeley.sbp;
import edu.berkeley.sbp.util.*;
import edu.berkeley.sbp.*;
@@ -7,15 +9,25 @@ import java.util.*;
import java.lang.reflect.*;
import java.lang.ref.*;
-/** an element which can produce one of several alternatives */
+/**
+ * an element which can produce one of several alternatives.
+ *
+ *
+ * Unlike the other Elements, Union is not immutable once
+ * constructed. To simulate this desirable feature, it is immutable
+ * once examined by taking its iterator or calling contains().
+ */
public class Union extends Element implements Iterable {
- private final String name;
+ private final String name;
private final boolean synthetic;
+ private boolean viewed = false;
private final List alternatives = new ArrayList();
public Union(String name) { this(name, false); }
+ public Union(String name, Sequence s) { this(name, s, false); }
+ public Union(String name, Sequence s, boolean synthetic) { this(name, synthetic); add(s); }
/**
* Since every cycle in a non-degenerate grammar contains at
@@ -31,39 +43,55 @@ public class Union extends Element implements Iterable {
this.synthetic = synthetic;
}
- public boolean contains(Sequence s) { return alternatives.contains(s); }
- public Iterator iterator() { return alternatives.iterator(); }
+ public boolean contains(Sequence s) {
+ viewed = true;
+ return alternatives.contains(s);
+ }
+
+ /** iterator over this Union's Sequences */
+ public Iterator iterator() {
+ viewed = true;
+ return alternatives.iterator();
+ }
/** adds an alternative */
- public void add(Sequence s) {
- if (alternatives.contains(s)) return;
+ public Union add(Sequence s) {
+ if (viewed)
+ throw new RuntimeException("once Union.contains() or Union.iterator() has been invoked, "+
+ "you may not add any more Sequences to it\n "+
+ " union in question: " + this);
+ if (s.needed_or_hated)
+ throw new RuntimeException("you may not add a conjunct directly to a Union");
+ s.in_a_union = true;
+ if (alternatives.contains(s)) return this;
alternatives.add(s);
+ return this;
}
+ /** adds a one-element sequence */
+ public void add(Element e) {
+ add(Sequence.create(e));
+ }
- // Epsilon Form //////////////////////////////////////////////////////////////////////////////
-
- // FIXME
- private Forest.Many epsilonForm = null;
- Forest epsilonForm() {
- if (epsilonForm != null) return epsilonForm;
- epsilonForm = new Forest.Many();
- for(Sequence s : this) {
- // FIXME FIXME FIXME
- if (new Walk.Cache().possiblyEpsilon(s))
- epsilonForm.merge(s.epsilonForm());
- }
+ /** the Forest which results from matching this Union against the empty string at region region */
+ Forest epsilonForm(Input.Region region) {
+ viewed = true;
+ Forest.Many epsilonForm = new Forest.Many();
+ for(Sequence s : this)
+ if (Element.possiblyEpsilon(s))
+ epsilonForm.merge(s.epsilonForm(region));
return epsilonForm;
}
// Display //////////////////////////////////////////////////////////////////////////////
- public String getName() {
- if (name != null) return name;
- return "(anon_union)";
- }
+ boolean isSynthetic() { return synthetic; }
+ String getName() { return name==null ? "(anon_union)" : name; }
+
public String toString() {
+ // technically this should be turned on, but we don't make a big deal
+ //viewed = true;
if (name != null) return name;
StringBuffer sb = new StringBuffer();
sb.append("(");
@@ -71,7 +99,11 @@ public class Union extends Element implements Iterable {
sb.append(")");
return sb.toString();
}
+
+ /** display this union in long/expanded form */
public StringBuffer toString(StringBuffer sb) {
+ // technically this should be turned on, but we don't make a big deal
+ //viewed = true;
if (synthetic) return sb;
boolean first = true;
String before = StringUtil.pad(15, getName()) + " = ";
@@ -87,6 +119,7 @@ public class Union extends Element implements Iterable {
}
private void bodyToString(StringBuffer sb, String before, String between) {
+ viewed = true;
boolean first = true;
for(Sequence s : this) {
// FIXME: what to do here about printing out negated sequences?